The present invention relates to reproducing apparatus for playing back data from a disc-shaped storage medium, particularly but not essentially audio data, and to such apparatus having means for displaying to a user data relating to the playback operation.
Players and recorders for storage discs, whether optical or magnetic (or a combination of both) are well known. At the mechanical level, these devices typically comprise a replay stage comprised of a spindle motor arranged to rotate a received disc at a controlled rate together with a traversal stage moving a read head across the tracks of the disc as it rotates. The discs, particularly but not exclusively those formatted according to CD Audio, CD-ROM, or DVD standards, carry a table of contents (TOC) which is read by the player on start-up and typically stored in local memory. The TOC identifies to the player where particular files are stored on the disc and enables the read head to be moved to access specific files or file segments.
One example of such a disc player is given in European patent application EP-A-0 768 660 in which, whilst the disc is being rotated, the target or desired address for the disc is compared with the actual read address to produce an error signal for compensating for linear velocity deviations.
Another example, in the form of a combined magnetic and optical disc reader, is described in U.S. Pat. No. 5,477,516. With this apparatus, a data stream is recorded on the disc in the form of discrete segments distributed across the disc. To enable fast seek and rewind functionality, the system described uses the TOC to build a linked list of the locations for the sequential parts of a file, with the system simply stepping through this list during high speed operation.
A typical feature of such disc players is a user display showing an identifier for the currently read file, together with ancillary data. In the case of an audio disc player, this identifier may comprise a track number and the ancillary data may comprise elapsed time for the track. This data is derived from subcodes in the file being read and by reference to the TOC.
A problem with such displays, however, arises during so-called trick-modes (fast forward/rewind) when the subcodes cannot generally be read fast enough and so the display cannot provide an accurate indication to the user of where the read head currently lies. The problem can also occur at slower speeds if the system is only configured to process the subcodes at one or just a limited range of preset speeds.
It is accordingly an object of the present invention to provide a disc reproducing apparatus having a user display the contents of which are kept up to date even at non-standard speeds.
In accordance with the present invention there is provided a disc reproduction apparatus comprising a disc replay stage operable to receive a disc and read data stored thereon, a controller coupled with the replay stage and a first storage means holding a table of contents for a received disc, and a display coupled to the controller, with the controller being configured to generate and periodically update for display an indication of data currently being read from a received disc based on indicator subcodes read from the disc and the table of contents; characterised in that the apparatus further comprises a time signal source coupled to the controller and the controller is arranged to generate and update an emulation model of a disc being read based at least partially on the table of contents and the time signal with the displayed indication of data being based instead on said emulation model when the indicator subcodes are unavailable. By providing the emulation model and periodically updating it (for example once per second of real disc play time) the display may be kept up to date even when the replay stage is in a fast seek mode during which subcodes cannot be read from the disc.
The replay stage suitably comprises a spindle motor arranged to rotate a received disc, a read head, and a scanning mechanism arranged to move the read head relative to the rotating disc under direction of the controller: the disc may be optical or magnetic and such a read head of the apparatus will be configured accordingly. The apparatus may further comprise user-operable input means coupled with said controller in response to the operation of which the relative motion between the head and disc may be varied. In such an arrangement, for one or more predetermined user-directed patterns of relative motion between head and disc said indicator subcodes may be read from the disc and, for all other user-directed patterns, the displayed indication may instead be based on said emulation model.
The or a predetermined user-directed pattern of relative motion may be such as to give a fixed replay rate for the recorded data, and user-directed patterns of motion other than said predetermined pattern or patterns may include those which would give a slower or faster replay rate than said fixed replay rate and/or a reverse direction of replay.
Where the data stored on the disc is encoded audio data, the apparatus may further comprise data processing means arranged to receive, decode, and output the same. In such an arrangement, the apparatus may be arranged to mute the output of the decoded audio at replay rates other than said fixed replay rate. The encoding may be in accordance with MPEG audio protocols or other data storage schemes, as will be readily understood.
As will be described with reference to preferred embodiments hereinafter, the emulation model may be provided by the controller maintaining a pointer within the table of contents to the item last read as indicated by the read indicator subcodes, and moving said pointer on the basis of time signal inputs, the user-directed pattern, and stored information for each item in the table of contents. In such an arrangement, where the stored information for each item in the table of contents includes a running time, the emulation model may specify elapsed running time for a current item as derived from a user-directed replay rate and direction and the last read indicator subcode.
As a further feature, the replay stage scanning mechanism may be controlled to periodically relocate the position of the read head relative to the disc on the basis of the emulation model, such that overall seek times during trick modes may be kept down.
Further features of the present invention are recited in the attached claims, the disclosure of which is incorporated herein by reference, and to which the readers attention is now directed.